HELP!!!!!
Go to your local hobby store or hard ware with your mom. Tell her you have a school project and need her to buy some supplies.
Get some modelling clay, plaster of Paris.
Use the clay to make a mold of your erect penis. Get hard, tie something around the base of your penis. That will keep it hard while you form the clay around it. Use lots of clay so it's thick and holds its shape.
Get the plaster ready, follow directions, not too thick, not thin. Untie your clock, the trapped blood rushes out, gets smaller so you can slip out of the clay mold. Coat your clock with oil or vasoline before you squeeze the clay around it.
Pour the plaster in the clay mold, wait for it to harden. Best left alone over night.
I used a lot of clay and after I had it firmly squeezed to form my penis I stuck it in an empty tall tea glass. Anything will work as long as it's a tight fit so the mold doesn't fall over or collapse.
After it dries completely, peel away the clay, sand, fill in voids with new plaster, paint with a good paint. Google that part, painting plaster o Paris.
Note, when you use it in your ads put a rubber on it or kitchen plastic wrap. I like veg oil or Crisco cooking grease.
Enjoy bro.
P.S. it might take some anal training to accomplish it
Im 14 and I like to do the same thing. I've experimented with many different things. I've used brushes, pens, a cucumber, my hand, and even a plastic ball (which probably isn't the best thing to use). The current thing I use is a plastic perfume bottle that's big enough and it feels good.